The U.S. Government is scrapping an airport security check which blew air at passengers and analyzed the results for traces of explosives. The system proved unreliable and costly to maintain.

The Transport and Security Administration bought 207 of the ‘puffer’ machines from General Electric and Smiths Administration in 2004. Only 94 of the machines ever made it into airports (34 locations across the country), with the rest remaining in storage. They had been set to be deployed as part of a rollout but this was put on hold after problems with the initial deployments.

The concept of the machines – officially known as explosive trace portals – was simple enough: they blew a puff of air onto a passenger, then immediately sucked it back. This air was then analyzed and the machines could detect particles of explosives as small as a billionth of a gram. The entire process could take as little as 17 seconds per passenger.

The problem is that, while the technology worked fine in perfect lab conditions, it couldn’t hold up to the rigors of a real life situation, particularly a busy airport. The machines broke down earlier and more often than expected, apparently due to the excessive dirt and moisture which builds up in a place where so many people pass through. The repair bill to date has topped $6 million, around a fifth of the total money spent on buying the machines.

So far 61 machines which have broken down have been withdrawn. The remaining 33 will be gradually phased out. The plan is to replace them with full body scanners.

Writing on its blog, the TSA noted that it has now opened a dedicated testing facility at Ronald Reagan National Airport which is better designed to test security technology and techniques in a more realistic environment.